Electrode assembly for compensating thermal expansion in an electrolytic cell

ABSTRACT

An electrode assembly removably mounted between next adjacent electrolytic cells in an arrangement or a succession of individual cells capable of compensating for thermal expansion of the individual cells. The assembly comprises a rigid plate and a flexible membrane spaced in opposed relationship defining opposed walls of next adjacent cells. The rigid plate has plate electrodes secured thereon disposed vertically in spaced positions functioning as cathodes of a preceding one of next adjacent cells and the flexible membrane, which effects the thermal expansion compensation, has plate electrodes removably mounted relative thereto disposed vertically in spaced positions functioning as the anodes of the succeeding cell of the next adjacent cells and likewise supported on the rigid plate.

United States Patent Apr. 25, 1972 Schoberle [54] ELECTRODE ASSEMBLY FOR COMPENSATING THERMAL EXPANSION IN AN ELECTROLYTIC CELL [72] Inventor: Robert Schoberle, l4 Willem van Criepstraat, Roermond, Netherlands [22] Filed: Nov. 21, 1969 [21] Appl. No.: 878,705

[30] Foreign Application Priority Data Nov. 22, 1968 Netherlands ..66463 [52] US. Cl ..204/286 [51] Int. Cl ..B0lk 3/04 [58] Field of Search ..204/286, 268, 254, 255, 256

[56] References Cited UNITED STATES PATENTS 3,119,759 1/1964 Hoover ..204/256 X FOREIGN PATENTS OR APPLICATIONS 575,665 5/1959 Canada ..205/254 Primary Examiner-Winston A. Douglas Assistant Examiner-M. J. Andrews Attorney-Robert E. Burns and Emmanuel J. Lobato [57] ABSTRACT An electrode assembly removably mounted between next adjacent electrolytic cells in an arrangement or a succession of individual cells capable of compensating for thermal expansion of the individual cells. The assembly comprises a rigid plate and a flexible membrane spaced in opposed relationship defining opposed walls of next adjacent cells. The rigid plate has plate electrodes secured thereon disposed vertically in spaced positions functioning as cathodes of a preceding one of next adjacent cells and the flexible membrane, which effects the thermal expansion compensation, has plate electrodes removably mounted relative thereto disposed vertically in spaced positions functioning as the anodes of the succeeding cell of the next adjacent cells and likewise supported on the rigid plate.

6 Claims, 4 Drawing Figures Patented Apr-i125, 1972 3,658,686

2 Sheets-Sheet 1 AF; 1A;

Patented April 25, 1972 2 Sheets-shat 2 ELECTRODE ASSEMBLY FOR COMPENSATING THERMAL EXPANSION IN AN ELECTROLYTIC CELL This invention relates generally to electrolytic cells and more particularly to a device for compensating the thermal expansion thereof.

In conventional multiple electrolytic cells in which a plurality of individual cells are arranged in a succession, special devices must be used to compensate for the total overall thermal expansion due to the additive expansion of the individual or elementary cells. Special tie rods and compensating springs are used, for example, in such apparatus. These compensating devices are relatively expensive and the number of elementary cells that can be handled by the springs is limited in view of their limited capacity. Moreover, to compensate for the additive expansion of the individual cells, flexible inlet and discharge pipes or ducts must be used to introduce and discharge the electrolyte and the products of electrolysis. The necessity of using flexible pipes results in leakage and renders the construction of such conduits or pipes expensive. Because of this thermal expansion, flexible electrical conductors must be used at least at one end of the cell arrangement.

It is a principal object of the present invention to provide apparatus for compensating the thermal expansion of each individual electrolytic cell in a succession of cells to avoid any additive expansion.

Another object of the invention is to provide a new and novel electrode assembly that carries out compensation for thermal expansion and is constructed so that corrosion of the various conductor ports is minimized by keeping the different metals remote from the electrolyte and the products of electrolysis.

Still another object is to provide an electrode assembly in which the anodes are removably supported thereon so that a quick removal and change over of defective electrodes can be carried out.

According to the invention, the thermal expansion of nextadjacent electrolytic cells is compensated by an electrode assembly comprising a rigid plate and a flexible membrane disposed in opposed relationship and spaced from each other. The plate and membrane define the opposed walls of next-adjacent electrolytic cells. Cathode plates are secured to the rigid wall plate of a preceding cell by welding them thereon disposed perpendicularly to the wall surface and in an upright position. The anodes are similarly positioned relative to the flexible membrane and removably supported on the rigid plate. The flexible membrane is framed circumferentially and is freely able to flex to carry out compensation of thermal expansion. Each individual electrolytic cell in a succession or sequence of cells is provided with a flexible membrane so that the thermal expansion of each individual elementary cell is compensated and any additive thermal expansion problems are avoided.

Other features and advantages of the method of thermal compensation and device in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawings in which:

FIG. 1 is an elevation view, partly in section, of a multiplecell constructed from a plurality of elementary electrolytic cells provided with thermal expansion compensating means according to the invention;

FIG. 2, is a fragmentary sectional view on an enlarged scale taken along section line AA illustrating the assembly of two elementary electrolytic cells according to the invention;

FIG. 3, is an elevation sectional view of an expansion-compensating electrode assembly according to the invention; and

FIG. 4, is a plan view of the electrode assembly in FIG. 3.

The invention described is applied to electrolytic cells for electrolysis of sodium chloride from a sodium chloride brine or electrolyte. However, the invention is equally applicable to electrolytic cells used for any desired electrolysis resulting in the liberation of heat and thermal expansion of the cells.

According to the drawings, as illustrated in FIG. 1, a multiple electrolytic cell is constructed from a succession of individual electrolytic cells. Each of the basic electrolytic cells comprises a rigid tank 1 having a rigid bottom and opposed sides. The cells are mounted on a base 2 to which they may be secured. The cell tanks are preferably made of a synthetic resin constituting reinforced polyvinyl chloride, for example. The cells may be constructed, for example, having the dimensions of about 1,100 millimeters in height with a width of about 950 millimeters and 538 millimeters in length.

The brine for producing the electrolytic products is introduced into the individual cell tanks through an inlet pipe 3. The spent electrolyte and the products of electrolysis are discharged through a line 4. Each of the cells is provided with two flanges 5 for removably mounting and securing thereon a thermal expansion compensating electrode assembly, as hereinafter explained, and constituting the end walls of a preceding cell and a succeeding next-adjacent cell.

The thermal expansion-compensating electrode assembly comprises a cathode support plate 6 made, for example, of steel, having welded thereto on one side steel cathodes 7, of 3 mm thickness, and on opposite sides are mounted copper cross-pieces 8 to which is secured an anode support plate 9 likewise made of copper. The cathode support plate 6 and the anode support plate 9 are spaced relative to each other to allow access to steel mounting nuts 10 for the steel anodes 11 constructed as plates welded to supports or mounts 12 extending through a flexible membrane 13. The flexible membrane is disposed spaced from, and in opposed relationship, to the rigid support plate 6 so that the membrane and rigid support plate form the end walls of next adjacent primary electrolytic cells 1, as illustrated in FIG. 1.

The cathode supports 12 have a circular cross-section and are made of titanium. The flexible membrane 13 is likewise made of titanium sheet having a thickness in the order of 1 mm. The anodes 11 are made of titanium plated with an electrically conductive covering, for example, a platinum-iridium alloy or ruthenium oxide. The anodes have a thickness of about two millimeters and a surface area of about 0.55 square meters. The density of the conductive covering is 5 g/sq. meter. As illustrated in the drawings, each of the anodes is welded with titanium to three supports 12 and is disposed vertically similarly to the cathodes. The anodes 11 are offset relative to the cathodes 7, as illustrated in FIG. 4, in order that within each cell the anodes and cathodes are interleaved.

The supports 12 are mounted on the flexible membrane 13 by means of nuts 14 which compress collars l5 and are threaded on threads of the respective supports 12. The leakage of electrolyte is prevented by an annular seal 16 made of hypalon or another synthetic elastomer received in a groove 17. A blind bore is provided in each support 12 and a copper stud 18 is received therein. The studs extend through the anodic supporting plate 9 and are held in position by steel nuts 10 and steel washers l9 and press the supports 12 against the support plate 9. The nuts 10, washers l9 and the threaded nut 14 on the circular supports 12 and the seal 15 are mounted externally of the cells and, therefore, are not subject to the corrosion that would take place if they were mounted internally thereof as in the usual manner.

The flexible membrane or sheet 13 has its peripheral or v marginal portions fixed between a rigid frame 20 and a flange 5 of the cell to which the frame and membrane are bolted. The fluid tightness between the flange 5 and the flexible membrane 13 and between the rigid support plate 6 and its cell tank is insured by flexible seals 21, 21'.

Those skilled in the art will recognize that the electrode assembly for compensating thermal expansion may be provided with only one set of the electrodes, for example, the anodes. Moreover, the flexible membrane can be made of a synthetic polymer sheet such as polytetrafluorethylene sheets. These sheets must be supported in order to resist the fluid pressure and can be provided with an external support such as a metallic grid, not shown.

In order to apply electrical current to the cells a rigid supply conductor 22 and a rigid output conductor 22' are provided. These are secured to the endmost cells and electrically connected thereto to provide current to the anodes and cathodes of the cells which are electrically in series, as illustrated, since the electrode assembly members are electrically conductive.

Since the cumulative efi'ects of thermal expansion are eliminated, the construction of the individual electrolytic cells is simplified and the whole structure is strengthened. Each individual cell remains stationary and the need for tie rods, compensating springs, flexible pipes for the fluids and flexible electrical conductors at the ends of the cell are avoided. The number of individual cells that can be mounted in a series or succession is unlimited. 1

The spacing between the two electrode support plates 6, 9 is such that the access to the anode mount members is readily provided. The anode plates may be quickly removed individually to repair them, for example, to repair their active surfaces. There is no need to stop the electrolysis of the overall arrangement of cells and, therefore, downtime is avoided. The electrolysis can be continued by simply shortcircuiting the individual cell being worked on.

I claim:

1. A bipolar electrode for compensating for thermal expansion of separate electrolytic cells interconnected in electrical series with interfoliated flat metal anode members and flat cathode members, comprising a flexible impervious sheet defining in use a removable external sidewall of a separate electrolytic cell, a rigid conductive support spaced from in opposed relationship to said flexible impervious sheet mountable on another separate electrolytic cell next adjacent to the firstmentioned cell defining a removable external sidewall thereof, a set of parallel flat electrode members defining in use the cathode assembly of the last-mentioned cell and conductively mounted on one side of and perpendicularly to said support, a set of parallel flat metal members defining in use an anode assembly of the first-mentioned cell and removably mounted on the other side of and perpendicularly to said support, and conductive means fluid-tightly extending through said flexible impervious sheet mounting said anode assembly on said support.

2. A bipolar electrode assembly according to claim 1, wherein said flexible impervious sheet is a titanium sheet.

3. A bipolar electrode assembly according to claim 1, wherein said flexible impervious sheet is a polymer sheet.

4. A bipolar electrode assembly according. to claim I, wherein said rigid conductive support comprises two parallel metal support plates conductively joined, metal spacers joining said two metal plates, one of these metal plates disposed supporting said parallel flat electrode members, the other metal plate removably supporting said anode assembly.

5. A bipolar electrode assembly according to claim 1, wherein said parallel flat electrode members consist of steel plates secured to said rigid conductive support.

6. A bipolar electrode assembly according to claim I, wherein anode assembly consists of activated titanium plates and said conductive means consist of titanium plugs secured to said titanium plates on the edge thereof, and means to insure fluid tightness with said flexible impervious sheet secured to said rigid conductive support. 

2. A bipolar electrode assembly accordiNg to claim 1, wherein said flexible impervious sheet is a titanium sheet.
 3. A bipolar electrode assembly according to claim 1, wherein said flexible impervious sheet is a polymer sheet.
 4. A bipolar electrode assembly according to claim 1, wherein said rigid conductive support comprises two parallel metal support plates conductively joined, metal spacers joining said two metal plates, one of these metal plates disposed supporting said parallel flat electrode members, the other metal plate removably supporting said anode assembly.
 5. A bipolar electrode assembly according to claim 1, wherein said parallel flat electrode members consist of steel plates secured to said rigid conductive support.
 6. A bipolar electrode assembly according to claim 1, wherein anode assembly consists of activated titanium plates and said conductive means consist of titanium plugs secured to said titanium plates on the edge thereof, and means to insure fluid tightness with said flexible impervious sheet secured to said rigid conductive support. 